A large number of people suffering from diabetes use some form of daily insulin therapy to maintain close control of their glucose levels. Currently, there are two principal modes of daily insulin therapy. The first mode includes syringes and insulin pens. These devices are simple to use and are relatively low in cost, but they require a needle stick at each injection, typically three to four times per day. The second mode includes infusion pump therapy, which entails the purchase of an insulin pump that lasts for about three years. The initial cost of the pump can be significant, but from a user perspective, the overwhelming majority of patients who have used pumps prefer to remain with pumps for the rest of their lives. This is because infusion pumps, although more complex than syringes and pens, offer the advantages of continuous infusion of insulin, precision dosing and programmable delivery schedules. This results in closer blood glucose control and an improved feeling of wellness.
An infusion pump is but one part of an assembly of infusion elements, which work together to deliver insulin or other medicament to an infusion site. Some elements are disposable, such as the infusion set or pump set which conveys the insulin from a reservoir within the pump into the skin of the user. An infusion set typically consists of a pump connector, a length of tubing, and a hub or base from which an infusion needle, flexible cannula or catheter extends. The hub or base has an adhesive which retains the base of the set on the skin surface during use, which may be applied to the skin manually or with the aid of a manual or automatic insertion device.
As noted above, infusion sets allow diabetic patients to infuse insulin via an infusion pump. To do so, infusion sets use one or more of an infusion needle, flexible cannula or catheter. For example, a steel infusion needle can be used to infuse insulin under the skin surface, either into the subcutaneous or intradermal skin layers, but may irritate the insertion site if moved. Alternatively, a soft, Teflon-based catheter can be provided with the infusion set to infuse insulin under the skin surface, usually into the subcutaneous skin layer, and is associated with less irritation than a steel cannula. However, soft cannulas or catheters are prone to kink which can delay or interrupt the insulin delivery and reduce therapy.
Most soft cannula or catheter infusion sets are inserted using another commonly associated element of infusion sets, a steel introducer needle that is positioned inside the catheter lumen and which extends beyond the catheter to initiate penetration. At insertion and placement, the introducer needle and catheter are both inserted into the infusion site either concurrently with or subsequent to adhesive placement of the infusion set to the skin surface. The introducer needle is then removed from the catheter after penetration, leaving the catheter in place.
Some infusion sets also provide and use a separate spring-loaded inserter that propels the infusion set and/or the introducer needle and catheter into the tissue at a desired speed and to a desired depth. Many such spring-loaded inserters further provide features to automatically retract or shield the introducer needle. Once in place, an infusion set is typically attached to a medicament supply using still another element, such as a length of tubing, which can be subject to inference and adversely affect the infusion set.
Accordingly, each element of the infusion set needs to operate separately and in combination, in an optimal manner. Otherwise, the performance of the infusion set can be adversely affected through the poor performance of individual elements of the infusion set.